The invention relates to an outer shell for an at least two-shell joint socket of a hip joint prosthesis, wherein the outer shell comprises a plurality of through-holes which are designed for the receipt of fastening elements for the fastening of the outer shell in a bone seat and which are each implemented with a counter-sink formed on the inner side of the outer shell.
The invention further relates to a hip joint prosthesis implemented with an outer shell of this kind and also to closure plug of an outer shell of this kind.
A joint socket of the named kind is described in CH-PS 674 927 and comprises a metallic outer shell and a plastic inner shell fittable therein, the socket is provided with a metallic dividing layer in the region of the through-holes which perforate the outer shell, this layer being in the form of a shell body formed from a metal sheet and fitted into the outer surface of the inner shell. Creep or cold flow of the plastic of the inner shell into those through-holes of the outer shell which remain free of fastening elements is intended to be prevented by this dividing layer to avoid direct contact between the bone tissue and rubbed-off plastic which may occur in the region of these through-holes. The relatively complicated three-part construction of the known joint socket requires stocking of a corresponding number of different shell bodies for the construction of the corresponding dividing layers, this is especially so for embodiments in which a supply of outer and inner shells with various grades of sizes are stocked.